Grinding disk



June 11, 1935. c. KRUG 2,004,630

GRINDING DISK Filed March so, 1934 Carl K709 mrvzw+c ra i; TT'

Patented June 11, 1935 GRING DISK Carl Krug, Frankfort-on-the-Main,Germany Application March 30, 1934, Serial No. 718,133 In GermanyDecember 6, 1932 the periphery of the grinding disk, this strain rapidlydecreases. It has now been recognized that an increase in the strengthof the annular zone near the wall of the aperture very efiectivelyreduces the dangerous strains and leads to an equalization of the strainover the entire cross section of the grinding disk, so that the risk offracture of the grinding disk is reduced.

With a view to increasing the tensile strength of the material of thegrinding disk it has already been proposed to incorporate materials ofdifferent nature such as metal insertions or reinforcements in theannular zone. Also in one and the same grinding disk grinding materialsof difierent qualities which vary in respect of the nature and magnitudeof the grinding granules or the nature and quantity of the bindertherefor have been employed without attaining the desired end.

According to the present invention the resistance of the annular zonenear the wall of the aperture to the action of the centrifugal forces isaugmented by increasing the tensile strength of the material of thegrinding disc by an auxiliary treatment, which does not alter the basicstructure of the grinding disk in this zone. This is effected forexample in that near the wall of the aperture the grinding disk isprovided with an additional binder for the grinding granules so that thegrinding disk has the basic structure uniformly throughout and issubjected to the supplementary treatment only at the annular zone, i.e., near the wall of the aperture. This is best effected by impregnatingand hardening of the disk in the vicinity of the wall of the aperture bymeans of a solution of artificial resin, which is available commerciallyunder the registered trade-mark Bakelite.

This measure is directly permissible because the parts of the grindingdisk near the wall of the aperture which are subjected to reinforcementare not employed for the grinding operation in view of the mechanicalmeans serving for securing the disk on the grinding shaft, so that theauxiliary treatment thereof cannot detrimentally afiect the grindingoperation.

The new efiect of the grinding disks produced in accordance with theinvention is based on the fact that without detriment to the reliabilityof operation they can rotate far more rapidly than hitherto and thusafiord a higher output. 1n addition, as the high annular strain at thewall of the aperture is considerably reduced and the lower annularstrain at the periphery of the grinding diskis correspondinglyincreased, an approximately uniform distribution of the strain over thecross section of the grinding disk is attained, which gives increasedreliability.

Two embodiments of the invention are shown by way of example in theaccompanying drawing, in which:

Fig. 1 shows a side view and Fig. 2 a, cross sectional view of agrinding disk which is adapted for use only on a correspondinglyconstructed grinding machine.

Fig. 3 shows a side view and Fig. 4 a cross sectional view of a grindingdisk the wall adjacent the aperture of which is arranged to accommodatethe flange fastening which is customarily provided on grinding machines.

In the embodiment according to Figs. 1 and 2, I is the grinding disk, 2the annular zone which has been reinforced by impregnation with asolution of artificial resin (bakelite) and hardening,

ing disk which can be mounted between theflanges of existing machineswithout any alteration thereto in the same way as the ordinarycommercial grinding disks. For this purpose the grinding disk I isrecessed on both sides to the size of the annular zone 2 which isimpregnated with artificial resin and hardened. In this way recesses 5,6 are obtained which accommodate the securing flanges. In this way thegrinding disk is clamped solely at the point of increased rigidity.

I claim:

1. A grinding wheel of uniform basic structure which has an arbor holetherethrough and which has an outer zone and a relatively narrow innerannular zone adjacent the arbor hole to which has been added astrengthening material throughout the thickness of the wheel, the outerzone being unchanged.

2. A grinding wheel of uniform basic structure which has an arbor holethroughout and which has an outer zone and a relatively narrow innerannular zone adjacent the arbor hole impregnated throughout thethickness of the wheel with a strengthening material, the outer annularzone being unimpregnated and unchanged.

3. The grinding wheel as set forth in claim 2, in which thestrengthening material is a synthetic resin.

4. The grinding wheel as set forth in claim 2, in which thestrengthening material is a phenolic condensation product. 1

\ CARL KRUG.

